Method for the manufacture of chlorates and perchlorates of alkali metals.



A. E. GiBBS.

METHOD FOR THE MANUFACTURE OF CHLORATES AND PERCHLORATES 0F ALKALI METALS.

APPLlCATlON FILED MAY 5, 1915.

1,1733%. Patqnted Feb.29,1916.

v a. $0. WQZM operation, sodium chlorid is supplied to the tank 10 to keep the solution saturated to as high a degree as is practicable-with that salt. After the liquors have circulated through the system a number of times, the chlorate gradually increases in amount and the liquor is then removed and concentrated for the recovery of the chlorate. The salt whlch separates out can be returned to the system.

cathode compartment of the cell, contains, in solution, sodium chlorid, sodium chlorate, caustic soda, and some carbonate of soda. The electrolyte in its passage through the cell has been depleted of some of its sodium ,chloridand this loss is made up by the addition of more sodium chlorid to the tank .10, as before described. A convenient way of getting this sodium chlorid into the solution is by means of the agitator 11. The grade of salt usually employed for this Work does not dissolve to a clear solution. It also usuallycontains some calcium, and magnesium salts.- This is precipitated in the tank 10 by the caustic and carbonated alkali. Some of this sediment or precipitate settles out at the bottom of the tank 10, and the remainder passes on to tank 13, in which it settles. These precipitates are drawn. off

at 14 and 15.

The precipitation of the lime or magnesia salts, which are usually present in the chlorid salts, added to the tank 10, is at the expense of some of the caustic or carbonated alkali present in this tank. The result of this, together with the removal of the chlorate from the solution at the bottom of the. tanks 10 and -13.is a deficiency of the alkali with respect to the chlorin produced in the cell, so that there is a sufficient excess of chlorin present in the absorption tower 17, to effect the conversion of hypochlorites to chlorates in said tower. If a pure - chlorid should be added in the tank 10, the

excess of chlorin would be maintained by withdrawing some alkaline liquor at either Potassium chlorate can be conveniently made by using a potassium chlorid, electrolyte, or a mixture of potassium andsodium chlorids in solution, or by adding potassium chlorid to the sodium chlorid electrolyte above described. .Double decomposition between the sodium chlorate and potassium chlorid takes place and the less soluble potassium chlorate separates out.

The chloratelof potash maybe removed either at 14 or 15. It is in the form of a sludge, and may then be purified in any usual way, as by placing it in a centrifuge to separate the caustic liquor from the chlo rate and from the insoluble mud precipitated from the commercial chlorid which is added at this point. The sludge can then the tank 13 to the tower 17 by any suitable connection. The operations for either chloq rate of soda or chlorate of potassium are The alkaline liquor coming from the' generally similar, except that in the case of the former, it being very soluble, does not crystallize in the vessels 10 or 13, but must be drawn off and concentrated. The sodium chlorid which separates out first can be returned to the system. By circulating the liquor through the cell a number of times, the proportion of chlorate to chlorid is greatly increased, and the solution going to the concentratorscan thus be made to contain more chlorate than chlorid. As the reaction between caustic and chlorin to produce chlorate is such that five molecules of chlorid are produced to one molecule of chlorate, this feature-is of great importance. The necessity of handling a large amount of chlorid for a small production of chlorate has causedthe commercial-abandonment of many other methods which have been tried.

It is obvious that many changes can be made in the apparatus used and in the details of the method described, without departing from the spirit and scope of my invention, as defined in the appended claims, thus, instead of one absorption tower several may be employed. Instead of removing the chlorate from the alkaline liquor,

I may remove it from the liquor at any other desirable point in the system. The alkali formed in the cathode compartment is not necessarily used to absorb chlorin,

since carbonate of soda or other cheaper alkali may be used for this the more valuable caustic a kal1 can be separated from the chlorate and chlorid, and sold or used as such. Similarly, if it is desirable to use the strong chlorin produced in the cell for purposes other than chlorate such as for making liquid chlorin, I can replace the amount .so used with chlorin from another sourceor produced by chemical means. But whatever the source of the alkali and chlorin, I prefer to supplythese to the system outside of the cell in such proportions that the chlorin is in excess, the chlorate and chlorid thus produced being returned to the electrolytic cell. If a mercury or gravity type of cell is used, Iprefer to filter or thoroughly settle the liquors containingthe chlorate, in order to avoid the danger caused by the presence of carbonaceous matter in the chlorate. If a cell is used with a mercury urpose, and I cathode some or all of the solution contain- 30 I claim:

1 1. The herein described method of making chlorate and chlorid is allowed to pass to the cathode compartment, preferably from the anode compartment, where it is decomposed by the sodium in the mercury, forming caustic soda and hydrogen, the chlorate being substantially unaltered. By continuing the electrolysis sufficiently, or by using a chlorate for the electrolyte and lowering the temperature, perchlorates can be made in the cell without using an outside absorption system. y

Some of the advantages resulting from my invention are as follows: The operation can be carried out at a temperature considerably in excess of 40 centig'rade Without causing. undue corrosion of the electrodes. As the conductivity of wet electrolytes increases with the increase of temperature, the cell can be run at a lower voltage at the higher temperature. The addition to the electrolyte of 'chromic acid or its salts can be dispensed with. Power efiiciency exceeding 52% of the theoretical efiiciency can be obtained, assuming the decomposition voltage of sodium chlorid to be 2.02 volts. When carbon or graphite anodes are used in connection with a diaphragm cell, contamination of the chlorate with carbonaceous matter is prevented. The grinding of chlorate is attended with considerable danger; and this danger is greatly increased if carbonaceous matter is present. The diaphragm being an excellent filter removes from the system all of the carbon or graphite which disintegrates from the electrodes.

The removal of the chlorate from the elec-.

trolyte is accomplished without disengaging or losing chlorin and without discomfort to the workmen. This is because the chlorate is removed from the system at a point between the electrolyzing apparatus and the absorption chamber Where there is no chlorin present and the strong alkaline liquor is free from-odor or corrosive action on iron.

The solution containing chlorate being strongly alkaline and substantially free reducing action of the hydrogen, the chlO- rate subjected to the action of nascent hydrogen being always in the cathode compartment and strongly alkaline. is not reduced to any appreciable extent by nascent hydrogen if the solution is alkaline.

The loss of efficiency which occurs in chlorate cells with secondary electrodes, due to the jumping of the current around some'of the electrodes, is avoided in my improved method.

Chlorate ing a chlorate, which consists in electrolyzher relatively to the amount-0f chlorin, to

thereby maintain an excess of chlorin in the combining chamber.

-2. The herein described method of making a chlorate, which. consists in electrolyzing a chlorid solution to produce chlorin and an alkali, uniting the chlorin and the alkali outside of the anode and cathode compartments of the electrolyzing apparatus, maintaining an excess of chlorin in the combining chamber, and returning the chlorate liquor resulting fromthe combination to the electrolyzing apparatus and repeating the described operations.

3. The herein described method of making a chlorate, which consists in electrolyzing a chlorid solution to produce chlorin and van alkali, uniting the chlorin and the alkali outside of the anode and cathode compartments of the electrolyzing apparatus,

maintaining an excess-of chlorin in the combining chamber, and returning the chlorate liquor resulting from the combination to the anode compartment of the electrolyzing apparatus.

4. The

herein described methodof maklyzing a chlorid vsolution to produce chlorin and an alkali,'discharging the alkali solution from the cathodeeompartment of the ing a chlorate salt, which consists in-electroelectrolyzing apparatus *andfthe chlorin from the anode compart1:le' mt' joit' the electrolyzing apparatus, adding, fresh chlorid to the alkali solution, and thenfbringingthe solution into [contac'twithfthe chlorin to produce a chlorate liquor. f H v 5. The. herein described'm'ethod of making a chlorate salt,'which con sis tsin electro-v lyzing a chlorid solution to produce chlorin and an alkali, dischargingthe alkali solution v fromthe cathode compartment fpf the elec trolyzing apparatus' and the chlorin; from the anode compartment of ithe electrolyzing appar'atus, adding freshchloriidto the alkali solution,-then bringing thesolution into coni tact with the chlorin to produce a chlorate 1 liquor, returning said liquor to "the anode compartment of the electrolyzing apparatus, and repeating the cyclef offIoperations, and

removing chlorate fIOm the lkaline liquor at 'a point in the system.. r mediate the electrolyzing apparatus and the absorption chamber where the chlorin and alkali are combined.

6.. The herein described method of making chlorate salt, Whichgconsists'in electrolyzing a chlorid solution in a. diaphragm-cell having carbon .or'graphite electrodes, to pro-- duce chlorin and an alkali liquor, withdrawing the chlorin fro-m the anode compartment of the electrolyzing apparatus, withdrawing the alkaline liquor' from the cathode compartment of the electrolyzing apparatus, uniting the chlorin and the alkaline liquor outside of both said compartments and circulating the chlorate liquor repeatedly through the cell to increase the proportion of the chlorate contained therein, and maintaining an excess of chlorin in the combining chamber.

7. The herein described method of making a chlorate salt, which. consists in electrolyzing a solution containing both a chlorid and a chlorate, the major portion of the chlorate passing to the cathode compartment of the electrolyzing apparatus without change, and the chlorid being electrolyzed therein to form chlorin and a caustic alkali, conducting the chlorin to an absorption chamber,

adding fresh chlorid to the alkaline solution discharged from the cathode compartment of the electrolyzing apparatus, and then bringing the alkaline liquor into contact with the chlorin, and removing chlorate from the system at a point between the electrolyzing apparatus and the absorption chamber.

8. The method of making a chlorate salt, which consists in electrolyzing a chlorid solution, bringing the alkaline liquor from the cathode compartment of the electrolyzing apparatus into contact with an excess of chlorin, outside of the anode and cathode 7i compartments of said apparatus, returning the chlorate containing solution to the said apparatus, and repeating the cycle of operathe cycle of operations until a perchlorate is produced in the alkaline liquor.

10. The method of making a perchlorate salt, which consists in electrolyzing a chlorid solution, bringing the alkaline liquor from the cathode compartment of the electrolyzing apparatus into contact with an excess of chlorin gas outside of the anode and cathode compartments of said apparatus, returning the resulting chlorate containing solution to the electrolyzing apparatus, repeating the 1 cycle of operations until a perchlorate is produced in the alkaline liquor, and removing the perchlorate from the system at a point intermediate the electrolyzing apparatus and absorption chamber.

In testimony whereof, I have hereunto set my hand.

ARTHUR- E. GIBBS.

Witnesses:

RALPH I. FEITERAZT, J. L. KEYsER. 

